Microplastics and the efficiency of their removal in rainwater treatment systems in Loess Plateau, Qingyang City, China

Rainwater runoff is the main way for microplastics (MPs) to enter water. We investigated a rainwater treatment system (RTS) located in Zhangtiegou, Qingyang City. They include constructed wetland 1 (SWF1), ecological ditch (EG), constructed wetland 2 (SWF2), and rainwater pond (RWP). Rainwater runoff originates from the urban area of Qingyang City. Samples were collected at each facility's inlet and outflow to determine the system's overall removal efficiency as well as the individual efficiency of each facility. Results indicated an MP abundance of 87 particles/L in stormwater runoff, with 74.50 % consisting of black fragment and 37.50 % being PVC. The total removal efficiency of MPs by the Rainwater Treatment System (RTS) was 73.56 %, with the SWF1 and SWF2 units achieving removal rates of 54.02 % and 86.84 %, respectively, while the EG unit only achieved 5 %. The RWP exhibited a cumulative scouring effect on MPs. The RTS demonstrated significant removal performance for ACR, EAA, PVB, PS, PP, and SIS, reaching 100 %, but the removal rates for PVC, PET, FKM, and PU were 50 %, 63.64 %, 71.43 %, and 75 %, respectively. Over all, these results demonstrate the potential for constructed wetland to prevent the migration of MPs to downstream.